Quick answer

GABA is the brain's main calming chemical messenger. Studies of GABA supplements used 100 to 300 mg for sleep and 20 to 100 mg for stress, and found small effects on how fast people fell asleep and on physical stress markers. The evidence is graded early, and whether GABA taken by mouth reaches the brain is unsettled.^1,2

Key facts

The body makes its own GABA from glutamic acid, another amino acid.¹
In the largest sleep trial, time to fall asleep dropped from about 13 to 6 minutes after four weeks of 300 mg a night.³
Blood GABA peaked 30 minutes after a 100 mg dose, but no study has shown it entering the human brain.^1,4
In a 2020 review, 11 of 14 studies on stress and sleep had authors employed by companies.¹

What GABA is

The body makes GABA from glutamic acid, and it is the main inhibitory chemical messenger of the brain and spinal cord.¹

Inside the brain, GABA works like a brake on nerve cells, making them less likely to fire. Sleep medicines such as benzodiazepines act on GABA's receptors. A supplement supplies GABA itself, which raises a different question, as the next section explains.¹

GABA occurs naturally in foods such as tea, tomatoes, soybeans, germinated rice and some fermented foods.^1,5

Adzuki beans contain about 2 g of GABA per kg and white tea about 0.5 g per kg, while fermented brown rice has about 10 to 100 mg per 100 g.^1,3

The GABA in the studies reviewed in 2020 was either made by fermentation with lactic acid bacteria or present naturally in foods; pharmaceutical-grade synthetic GABA was left out of that review.^1,3

Does GABA from a supplement reach the brain?

Whether GABA taken by mouth crosses from the blood into the brain is unsettled: studies disagree, and none has shown it happening in people.^1,2

This is the central question for GABA supplements, because GABA does its known job inside the brain. For decades, researchers thought it could not get there from the blood. Later studies contradict each other: some suggest only small amounts cross, others that more might, and their methods differ widely. A 2015 review concluded that how GABA supplements might act is far from clear.^1,2

Researchers have suggested that GABA might act through nerves in the gut that signal to the brain, rather than by entering the brain itself.^1,2

GABA certainly reaches the blood: levels peaked about 30 minutes after a 100 mg dose. What happens next, in people, has not been measured directly. The 2015 review pointed to brain scans that measure GABA as the way to settle it.^2,4

What the evidence shows

Each claim below carries a grade and the amount the studies used. Both are graded early: a handful of small studies, most with authors employed by companies, and no large trials.¹

May help you fall asleep a little faster when taken nightly for one to four weeks*^1,3,4,5

Early evidence

Three small studies measured sleep with overnight brain-wave recordings. In the largest, 40 adults who reported poor sleep took 300 mg of GABA from fermented rice germ or a placebo an hour before bed for four weeks; time to fall asleep dropped from about 13 to 6 minutes with GABA and did not change with placebo, though questionnaire scores did not differ between the groups. A one-week study of 10 people found faster sleep onset with 100 mg taken 30 minutes before bed, and a similar study of 16 found only a trend. A 95-day trial of 1.5 g a day in 52 adults aged 50 to 70 found no change in self-rated sleep. A 2020 systematic review rated the evidence for sleep as very limited, and one of the recording studies was run by a GABA maker.

Amount studied: 100 to 300 mg a day, taken 30 to 60 minutes before bed, for one to four weeks

May soften some physical signs of stress during a demanding mental task*^1,6,7

Early evidence

Eight small studies, with 7 to 63 people each, gave 20 to 100 mg of GABA, mostly as a single dose and often before a stressful task such as timed arithmetic. Several reported smaller stress-related changes than the comparison in markers such as heart rate variability, salivary chromogranin A, cortisol or brain-wave patterns, but most found no difference in how tense or relaxed people said they felt. A 2020 systematic review rated the evidence as limited, and 11 of the 14 studies it included had authors employed by companies.

Amount studied: 20 to 100 mg, mostly as a single dose, with effects measured within about an hour

What about muscle, growth hormone and men?

In 11 resistance-trained men, a single 3 g dose raised growth hormone about fourfold at rest compared with placebo; the authors note that the effect on muscle growth is unknown.⁸

In a 12-week trial run by a GABA maker, 21 men training twice a week gained more whole-body lean mass with 100 mg of GABA plus 10 g of whey a day than with whey alone, about 1.3 kg against 0.1 kg. Strength and arm and leg lean mass did not differ between the groups.⁹

A short rise in growth hormone after one large dose does not show that muscle grows faster, and the one trial that measured muscle found no difference in strength. Both studies enrolled men only. No claim about muscle is made here.^8,9

How much was used

Sleep studies gave 100 to 300 mg a day, taken 30 to 60 minutes before bed, for one to four weeks.^1,3

Studies of mental stress gave 20 to 100 mg, usually as one dose. Foods enriched with GABA, such as tea, rice and chocolate, supplied about 2 to 30 mg a serving.¹

No study has worked out a best amount. The dosage guide lists every amount tested in people, from the few milligrams in enriched foods to the gram doses used in research on hormones.^1,8

What's in ours

What’s in ours

Sleep: GABA, 100 mg per serving, from the label

Our Sleep formula lists 100 mg of GABA per serving, the lowest amount used in the sleep studies, alongside melatonin and herbs. Its product page makes no claim for GABA, because the trials were small and early.¹

Side effects, medicines, and who should ask first

In a four-week trial of 300 mg a night, 3 of 30 people on GABA reported mild stomach discomfort, headache or drowsiness, against 1 of 10 on placebo, who reported drowsiness. None of these effects was severe.³

At 2 g three times a day for a week, minor complaints became more common: sore throat, a burning feeling in the throat or on the skin, headache and dizziness. None was serious.¹⁰

Some studies found GABA can lower blood pressure. In 39 adults with mild high blood pressure, a fermented milk containing GABA lowered systolic pressure by about 17 mmHg over 12 weeks, more than placebo. A 95-day trial of 1.5 g a day in adults aged 50 to 70 found no significant change.^5,11

We found no official upper limit for GABA, and FDA has not finished evaluating it as a food ingredient. The largest amounts in the studies we read were a single 3 g dose and 2 g three times a day for one week, which brought only minor complaints.^8,10,12

None of the official sources we checked documents an interaction between GABA and a medicine: not the drug labels, MedlinePlus, LiverTox or NIH. That is not proof that a combination is safe. If you take a sedative, a sleep medicine, gabapentin, an antidepressant or blood pressure medicine, ask your pharmacist before adding GABA.

Ask first if you are pregnant or nursing, or under 18: the studies we found enrolled adults.¹
Ask first if you take medicine for diabetes, because 2 g doses raised insulin in healthy volunteers.¹⁰

Questions people ask

Does GABA make you sleepy?

Not reliably. In the four-week trial of 300 mg a night, one person on GABA and one on placebo reported drowsiness. The sleep studies measured how quickly people fell asleep after weeks of nightly use, not whether a dose made them feel drowsy.³

What does a GABA supplement do to the brain?

Inside the brain, GABA slows nerve signals. Whether a supplement adds to the brain's own GABA is not known: studies disagree on whether it crosses into the brain, and no human study has shown that it does. Small studies did record changes in brain-wave patterns within an hour of a 100 mg dose.^1,6,7

Is GABA the same as gabapentin?

No. Gabapentin is a prescription medicine shaped like GABA, but its label says it has no effect on how GABA binds, is taken up or is broken down. A GABA supplement is the messenger itself.¹³

Does GABA do anything for men in particular?

Nothing specific to men has been shown. The growth hormone and lean mass studies enrolled only men, and neither shows faster muscle growth, while the sleep and stress studies included both men and women.^3,6,8,9

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line Sleep

Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.